Which of the following settings do not prevent two pote……

多项选择题Routers R1 and R2, OSPF neighbors in area 0 over their Fa0 0 interfaces (respectively), currently both successfully use OSPF MD5 authentication. The OSPF configuration includes the area 0 authentication command under the router ospf 1 command. Which of the following commands must have been configur ed on R1s Fa0 0 interface?（）

A. ip ospf authentication null
B. ip ospf authentication message - digest
C. ip ospf authentication -key whatever- it - is
D. ip ospf message - digest - key 1 md5 whatever - it - is
E. ip ospf md5 1 key whatever - it - is

多项选择题Routers R1 and R2 are OSPF neighbors using their Fa0 0 interfaces, respectively, using default settings for all timers. An engineer ad ds the ip ospf hello - interval 6 command to R1s Fa0 0 configuration. Which of the following is true regarding the results from this change?（）

A. The show ip ospf neighbor command on R1 lists the revised Hello timer
B. The show ip ospf interfac e brief command on R1 lists the revised Hello timer
C. The R1 - R2 neighborship fails due to Hello timer mismatcH
D. The show ip ospf interface command on R1 lists the revised Hello timer

多项选择题Rout er R1 directly connects to subnet 10.1.1.0 24 with its Fa0 0 interface. R1 can ping four other working OSPF routers in that subnet. R1 is neither the designated router (DR) nor backup DR (BDR). OSPF is working correctly on all five routers. Which of the following is true on R1?（）

A. The show ip ospf neighbors command lists two neighbors off Fa0/0.
B. The show ip ospf neighbors command lists four neighbors off Fa0/0.
C. The show ip ospf neighbors command lists two neighbors off Fa0/0 in the FULL state.
D. The show ip ospf neighbors command lists two neighbors off Fa0/0 in the DISCO state.

多项选择题Which of the following can either directly or indirec tly identify all the interfaces for which both 1) OSPF has been enabled and 2) OSPF is not passive?（）

A. show ip ospf database
B. show ip ospf interface brief
C. show ip protocols
D. show ip route ospf
E. show ip ospf neighbors

单项选择题Which of the following is true about an OSPF area border router (ABR)?（）

A. The ABR must have multiple interfaces connected to the backbone areA
B. An ABR is a router with two interfaces, each connected to a different nonbackbone areA
C. The only requirement to be considered an  ABR is at least one interface connected to the backbone areA
D. An ABR must have at least one interface in the backbone area plus at least one other interface in a nonbackbone areA